U.S. patent number 8,334,737 [Application Number 12/836,867] was granted by the patent office on 2012-12-18 for acoustic wave device and electronic apparatus using the same.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Koji Kawakita, Eiji Kawamoto, Toru Yamaji.
United States Patent |
8,334,737 |
Yamaji , et al. |
December 18, 2012 |
Acoustic wave device and electronic apparatus using the same
Abstract
An acoustic wave device includes a piezoelectric substrate, an
IDT electrode on the substrate, an internal electrode above the
substrate, a side wall above the internal electrode, a lid on the
side wall, an electrode base layer on the internal electrode, a
connection electrode on the electrode base layer, and an
anti-corrosion layer between the internal electrode and the side
wall. The internal electrode is electrically connected to the IDT
electrode. The side wall surrounds the IDT electrode. The lid
covers the IDT electrode to provide a space above the IDT
electrode. The electrode base layer is provided outside the space
and the side wall. The anti-corrosion layer protrudes outside the
side wall, and is made of material less soluble in plating solution
than the internal electrode. This acoustic wave device prevents the
internal electrode from breaking due to plating solution, hence
being manufactured at a high yield rate.
Inventors: |
Yamaji; Toru (Osaka,
JP), Kawakita; Koji (Nara, JP), Kawamoto;
Eiji (Osaka, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
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Family
ID: |
43464861 |
Appl.
No.: |
12/836,867 |
Filed: |
July 15, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110012695 A1 |
Jan 20, 2011 |
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Foreign Application Priority Data
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Jul 15, 2009 [JP] |
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2009-166540 |
Jul 15, 2009 [JP] |
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2009-166541 |
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Current U.S.
Class: |
333/193;
310/344 |
Current CPC
Class: |
H03H
9/02937 (20130101); H03H 9/1092 (20130101) |
Current International
Class: |
H03H
9/00 (20060101); H01L 41/00 (20060101) |
Field of
Search: |
;333/133,193,194,195,196
;310/313R,344,348 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2006/106831 |
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Oct 2006 |
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WO |
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Primary Examiner: Takaoka; Dean O
Attorney, Agent or Firm: RatnerPrestia
Claims
What is claimed is:
1. An acoustic wave device comprising: a piezoelectric substrate;
an interdigital transducer (IDT) electrode provided on the
piezoelectric substrate; an internal electrode provided above the
piezoelectric substrate and electrically connected to the IDT
electrode; a side wall provided above the internal electrode and
surrounding the IDT electrode; a lid provided on the side wall for
covering the IDT electrode to provide a space above the IDT
electrode; an electrode base layer provided on the internal
electrode and outside the space and the side wall; a connection
electrode provided on the electrode base layer; and an
anti-corrosion layer provided between the internal electrode and
the side wall, the anti-corrosion layer protruding outside the side
wall, the anti-corrosion layer being made of material less soluble
in plating solution than the internal electrode.
2. The acoustic wave device according to claim 1, wherein the
anti-corrosion layer is made of metal.
3. The acoustic wave device according to claim 1, wherein the
anti-corrosion layer is made of single metal of titanium, chrome,
molybdenum, tungsten, gold, or platinum, or made of alloy mainly
containing at least one of titanium, chrome, molybdenum, tungsten,
gold, and platinum.
4. The acoustic wave device according to claim 1, wherein the
anti-corrosion layer is made of insulating material mainly
containing silicon nitride, silicon oxynitride, or silicon
oxide.
5. The acoustic wave device according to claim 1, wherein the
anti-corrosion layer is made of metal oxide.
6. The acoustic wave device according to claim 1, wherein the side
wall has a lower surface facing the internal electrode, and the
anti-corrosion layer is provided between the entire lower surface
of the side wall and the internal electrode.
7. The acoustic wave device according to claim 1, wherein the side
wall further has an inner side surface facing the space and an
outer side surface opposite to the inner side surface, and the lid
is placed inside the outer side surface of the side wall.
8. An electronic apparatus comprising: the acoustic wave device
according to claim 1; a semiconductor integrated circuit connected
to the acoustic wave device; and a demodulator connected to the
semiconductor integrated circuit.
9. An acoustic wave device comprising: a piezoelectric substrate;
an interdigital transducer (IDT) electrode provided on the
piezoelectric substrate; a side wall provided above the
piezoelectric substrate and surrounding the IDT electrode and made
of resin; a lid provided on the side wall for covering the IDT
electrode to provide a space above the IDT electrode; a lid
reinforcing layer provided on the lid and made of plated metal; and
a side-wall reinforcing layer provided on the side wall, wherein
the side wall further has an inner side surface facing confronting
the space and an outer side surface opposite to the inner side
surface, and the side-wall reinforcing layer is made of plated
metal covering the outer side surface and is connected electrically
to the lid reinforcing layer.
10. The acoustic wave device according to claim 9, wherein the
side-wall reinforcing layer is made of single metal of copper,
gold, silver, platinum or nickel, or made of alloy mainly
containing at least one of copper, gold, silver, platinum, and
nickel.
11. The acoustic wave device according to claim 9, wherein the lid
is placed inside an outer edge where a upper surface of the side
wall connects with the outer side surface.
12. An electronic apparatus comprising: the acoustic wave device
according to claim 9; a semiconductor integrated circuit connected
to the acoustic wave device; and a demodulator connected to the
semiconductor integrated circuit.
Description
FIELD OF THE INVENTION
The present invention relates to an acoustic wave device and an
electronic apparatus, such as a portable phone, including the
device.
BACKGROUND OF THE INVENTION
FIG. 9 is a sectional view of conventional acoustic wave device
101, a chip-size packaged device. Acoustic wave device 101 includes
piezoelectric substrate 102, interdigital transducer (IDT)
electrode 103 provided on piezoelectric substrate 102, insulator
110 provided on piezoelectric substrate 102 for covering and
protecting IDT electrode 103 from the outside.
Acoustic wave device 101 further includes internal electrode 104
provided on piezoelectric substrate 102, side wall 105 provided on
internal electrode 104, lid 107 provided on side wall 105,
electrode base layer 109 provided on internal electrode 104, and
connection electrode 112 provided on electrode base layer 109.
Internal electrode 104 is made of, e.g. aluminum, and electrically
connected to IDT electrode 103. Side wall 105 surrounds IDT
electrode 103. Lid 107 is bonded to side wall 105 with adhesive
layer 106 for covering space 108 provided above IDT electrode 103.
Electrode base layer 109 is provided outside space 108 and side
wall 105, and is made of, e.g. copper. Connection electrode 112
extends through insulator 110 for electrically connecting external
electrode 111 to IDT electrode 103.
Connection electrode 112 has a columnar shape. Electrode base layer
109 is formed of metal thin film by a sputtering method. Then,
connection electrode 12 is formed by an electrolytic plating method
with electrode base layer 109 being energized.
In acoustic wave device 101, side wall 105 and internal electrode
104 may peeled off to produce a void between them. In this case,
electrode base layer 109 is not attached strongly to the boundary
between side wall 105 and internal electrode 104 when base layer
109 is formed by the sputtering. In such a case, internal electrode
104 is exposed from electrode base layer 109 at the boundary, so
that plating solution used in foregoing electrolytic plating
process corrodes internal electrode 104. As a result, internal
electrode 104 may be broken, accordingly reducing a yield rate of
acoustic wave device 101.
SUMMARY OF THE INVENTION
An acoustic wave device includes a piezoelectric substrate, an
interdigital transducer (IDT) electrode on the substrate, an
internal electrode above the substrate, a side wall above the
internal electrode, a lid on the side wall, an electrode base layer
on the internal electrode, a connection electrode on the electrode
base layer, and an anti-corrosion layer between the internal
electrode and the side wall. The internal electrode is electrically
connected to the IDT electrode. The side wall surrounds the IDT
electrode. The lid covers the IDT electrode to provide a space
above the IDT electrode. The electrode base layer is provided
outside the space and the side wall. The anti-corrosion layer
protrudes outside the side wall, and is made of material less
soluble in plating solution than the internal electrode.
This acoustic wave device prevents the internal electrode from
breaking due to plating solution, hence being manufactured at a
high yield rate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a top view of an acoustic wave device in accordance with
Exemplary Embodiment 1 of the present invention.
FIG. 1B is a sectional view of the acoustic wave device on line
1B-1B shown in FIG. 1A.
FIG. 1C is a further sectional view of an exemplary embodiment of
the present invention.
FIGS. 2A to 2J are sectional views of the acoustic wave device in
accordance with Embodiment 1 for illustrating process for
manufacturing the acoustic wave device.
FIG. 3 is a top view of an acoustic wave filter including the
acoustic wave device in accordance with Embodiment 1.
FIG. 4 is a top view of another acoustic wave filter including the
acoustic wave device in accordance with Embodiment 1.
FIG. 5A is a top view of an acoustic wave device in accordance with
exemplary Embodiment 2 of the invention.
FIG. 5B is a sectional view of the acoustic wave device on line
5B-5B shown in FIG. 5A.
FIG. 6 is a sectional view of the acoustic wave device on line 6-6
shown in FIG. 5A.
FIGS. 7A to 7I are sectional views of the acoustic wave device in
accordance with Embodiment 2 for illustrating processes for
manufacturing the acoustic wave device.
FIG. 8A is a top view of an acoustic wave filter including the
acoustic wave device in accordance with Embodiment 2.
FIG. 8B is a block diagram of an electronic apparatus in accordance
with Embodiments 1 and 2.
FIG. 9 is a sectional view of a conventional acoustic wave
device.
DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS
Exemplary Embodiment 1
FIG. 1A is a top view of an acoustic wave device in accordance with
Exemplary Embodiment 1 of the present invention. FIG. 1B is a
sectional view of the acoustic wave device on line 1B-1B shown in
FIG. 1A.
Acoustic wave device 1 is a chip-size packaged device and includes
piezoelectric substrate 2, interdigital transducer (IDT) electrode
3 provided on upper surface 2A of substrate 2, and insulator 10
provided on upper surface 2A of piezoelectric substrate 2 for
covering and protecting IDT electrode 3 from the outside.
Acoustic wave device 1 further includes internal electrode 4
provided on upper surface 2A of piezoelectric substrate 2, i.e.,
above upper surface 2A of piezoelectric substrate 2, side wall 5
provided on upper surface 4A of internal electrode 4, i.e., above
upper surface 4A of internal electrode 4, and lid 7 provided on
upper surface 5A of side wall 5. Internal electrode 4 is
electrically connects with IDT electrode 3. Side wall 5 surrounds
IDT electrode 3. Lid 7 is rigidly mounted onto upper surface 5A of
side wall 5 with adhesive layer 66 such that lid 7 covers space 8
provided above upper surface 3A of IDT electrode 3. Side wall 5 has
inner side surface 5C facing space 8 and outer side surface 5D
opposite to inner side surface 5C.
Acoustic wave device 1 further includes electrode base layer 9
provided on upper surface 4A of internal electrode 4, connection
electrode 12 provided on upper surface 9A of electrode base layer
9, and external electrode 11 provided on upper surface 10A of
insulator 10. Electrode base layer 9 is provided along outer side
surface 5D of side wall 5. Connection electrode 12 extends from
upper surface 9A of electrode base layer 9 to upper surface 10A of
insulator 10, hence extending through insulator 10 for electrically
connecting external electrode 11 to IDT electrode 3.
Acoustic wave device 1 further includes lid base layer 13 provided
on upper surface 7A of lid 7, and lid-reinforcing layer 14 provided
on upper surface 13A of lid base layer 13 for increasing mechanical
strength of lid 7.
Acoustic wave device 1 further includes anti-corrosion layer 15
provided between internal electrode 4 and side wall 5.
Anti-corrosion layer 15 protrudes from outer side surface 5D of
side wall 5 and is made of material which is less soluble in
plating solution than the material for internal electrode 4 is.
Piezoelectric substrate 2 is made of single-crystal piezoelectric
material, such as crystal, lithium tantalite, lithium niobate, or
potassium niobate. Substrate 2 has a thickness ranging from about
100 .mu.m to 350 .mu.m.
IDT electrode layer 3 includes comb-shaped electrodes having a
thickness ranging from about 0.1 .mu.m to 0.5 .mu.m, and is made of
single metal selected from aluminum, copper, silver, gold,
titanium, tungsten, platinum, chrome, or molybdenum. Layer 3 can be
also made of alloy mainly containing at least one of the metals, or
laminated metal containing the metals.
Internal electrode 4 is a conductor for electrically connecting
external electrode 11 to IDT electrode 3, and is made of single
metal of aluminum, copper, or silver. Electrode 4 can be made of
alloy containing mainly at least one of the metals, or laminated
metals.
Side wall 5 surrounds IDT electrode 3 at least partly, and has a
height ranging from about 5 .mu.m to 15 .mu.m. Side wall 5 is made
of insulating material, and preferably made of resin since the
resin can be processed to have a predetermined shape easily. To be
more specific, the resin can be photosensitive resin, such as
photosensitive polyimide resin, photosensitive epoxy resin, or
photosensitive acrylate resin, and allows side wall 5 to have a
predetermined shape accurately, which is necessary to form plural
acoustic wave devices 1 on piezoelectric substrate 2.
Photosensitive polyimide resin is preferable among others for side
wall 5 since this resin has a high glass transitional point and
high reliability in a high temperature environment.
Adhesive layer 66 is made of adhesive agent and has a thickness
ranging from about 1 .mu.m to 10 .mu.m. To be more specific, the
adhesive agent can be made of, e.g. epoxy-based resin,
polyphenylene-based resin, or butadiene-based resin. The adhesive
agent can be made of mixture resin containing the above resins.
Adhesive layer 66 is made of material having a bonding force per
unit area to insulator 10 than the material for side wall 5.
Lid 7 is a plate having a thickness ranging from about 1 .mu.m to
10 .mu.m and is bonded to upper surface 5A of side wall 5 with
adhesive layer 66. Lid 7 together with piezoelectric substrate 2
and side wall 5 accommodates IDT electrode 3. Lid 7 is preferably
made of metal because of its excellent mechanical strength and
electrical conductivity that allows controlling electrical
potential of lid 7. Copper for the material of lid 7 is more
preferable because copper has a liner expansion coefficient similar
to that of single crystal piezoelectric substrate 2. Lid 7 can have
a foil shape, and stuck on adhesive layer 66 previously formed on
the upper surface of side wall 5. This structure allows acoustic
wave device 1 to be handled easily during manufacturing
processes.
Space 8 is an airtight area surrounded by piezoelectric substrate
2, side wall 5, and lid 7, and accommodates IDT electrode 3
therein. Space 8 can be filled with air at a normal atmospheric
pressure; however, space 8 is preferably sealed and decompressed to
a pressure lower than the atmospheric pressure so as to prevent the
IDT electrode from corrosion.
Electrode base layer 9 is made of metallic thin film and formed on
upper surface 4A of internal electrode 4 and outside of side wall
5, i.e. opposite to space 8 with respect to wall 5. Electrode base
layer 9 is also formed on outer side surface 5D of side wall 5.
Electrode base layer 9 is made of single metal of titanium, copper,
nickel, chrome, or magnesium. Electrode base layer 9 can be made of
alloy mainly containing at least one of the metals. These materials
are less soluble in plating solution than the material for internal
electrode 4 is. Titanium among others is preferable for Electrode
base layer 9 because of its excellent adhesive properties. FIG. 1C
shows another structure of electrode base layer 9. As shown in FIG.
1C, Electrode base layer 9 can have a double-layer structure,
including titanium layer 509 and copper layer 609 provided on
titanium layer 509. Titanium layer 509 is made of titanium and
provided on upper surface 4A of internal electrode 4, upper surface
15A of anti-corrosion layer 15, and outer side surface 5D of side
wall 5. Copper layer 609 is made of copper. This structure allows
connection electrode 12 to be formed easily.
Insulator 10 is placed on upper surface 2A of piezoelectric
substrate 2 and outer side surface 5D of side wall 5, and on upper
surface 5A of wall 5 and upper surface 7A of lid 7. Insulators 10
together with side wall 5 surround connection electrodes 12.
Insulator 10 covers entirely upper surface 2A, i.e. a main surface
of piezoelectric substrate 2 so as to protect IDT electrode 3 and
others from mechanical shocks and moisture. Insulator 10 also
covers lid 7 and lid-reinforcing layer 14. Insulator 10 is
preferably made of thermosetting resin because of its excellence in
handling. Epoxy resin is more preferable to insulator 10 because of
its heat resistance and air-tightness. Epoxy resin containing
inorganic filler is more preferable to insulator since it lowers a
linear expansion coefficient of insulator 10. The inorganic filler
may employ aluminum oxide powder, SiO.sub.2 powder, or MgO
powder.
External electrode 11 is formed on upper surface 10A of insulator
10, i.e. outside of insulator 10, and is electrically connected
with connection electrode 12. According to Embodiment 1, insulator
10 is formed between external electrode 11 and side wall 5 to
prevent electrode 11 from directly contacting side wall 5.
Connection electrode 12 is formed by an electrolytic plating method
on internal electrode 4 via electrode base layer 9. Electrode 12 is
preferably made of copper since copper has large mechanical
strength and has a linear expansion coefficient identical to that
of piezoelectric substrate 2.
Lid base layer 13 is formed on lid 7 and made of metal thin film of
at least single metal of titanium, copper, nickel, chrome, or
magnesium. The metal thin film can be also formed of alloy mainly
containing at least one of the metals. Titanium among others for
layer 13 is preferable because of its excellent adhesiveness. Lid
base layer 13 can be in a double-layer structure including the
titanium layer and the copper layer similarly to electrode base
layer 9 shown in FIG. 1C. This structure is preferable because it
allows lid reinforcing layer 14 to be formed easily. Lid base layer
13 functions as a base coating for the electrolytic plating.
Lid reinforcing layer 14 is formed by the electrolytic plating
process on upper surface 13A of lid base layer 13, and has a
thickness ranging from about 20 .mu.m to 40 .mu.m. Lid reinforcing
layer 14 is preferably made of copper because copper has a large
mechanical strength and has a linear expansion coefficient
identical to that of piezoelectric substrate 2.
Anti-corrosion layer 15 is provided between internal electrode 4
and side wall 5, and protrudes from outer side surface 5D of wall 5
to the outside from top view. Anti-corrosion layer 15 has a
thickness ranging about 0.01 .mu.m to 1 .mu.m. Anti-corrosion layer
15 is made of material less soluble in plating solution than
material of internal electrode 4. Anti-corrosion layer 15 is not
necessarily made of metal; however, metal reduces an ohmic loss of
layer 15. The metal can be at least one single metal of titanium,
chrome, molybdenum, tungsten, gold, or platinum. Anti-corrosion
layer 15 can be also made of alloy mainly containing the above
metals. Titanium among others is preferable for layer 15 because it
has high adhesiveness and yet low solubility in the plating
solution. Anti-corrosion layer 15 can be made of insulating
material mainly containing, e.g. silicon nitride, silicon
oxynitride, or silicon oxide.
A void may be produced between side wall 5 and internal electrode
4, so that the void prevents electrode base layer 9 from adhering
strongly enough to the boundary between side wall 5 and internal
electrode 4. Even in this case, anti-corrosion layer 15 formed
between electrode 4 and wall 5 prevents internal electrode 4 from
being corroded by the plating solution used during the electrolytic
plating process which forms connection electrode 12. This
arrangement prevents internal electrode 4 from breaking,
accordingly raising the yield rate of acoustic wave device 1.
Anti-corrosion layer 15 made of metal oxide, such as titanium
oxide, roughens the surface of anti-corrosion layer 15, hence
adhering to side wall 5 securely.
Anti-corrosion layer 15 can be provided only between internal
electrode 4 and an edge where lower surface 505B is connected with
outer side surface 5D of side wall 5. This arrangement reduces an
ohmic loss caused by anti-corrosion layer 15. Anti-corrosion layer
15 made of metal between entire lower surface 505B of wall 5 and
internal electrode 4 increases the adhesiveness between electrode 4
and side wall 5.
A method for manufacturing acoustic wave device 1 in accordance
with Embodiment 1 will be described below. FIGS. 2A to 2J are
sectional views of acoustic wave device 1 for illustrating
processes for manufacturing acoustic wave device 1.
First, as shown in FIG. 2A, plural IDT electrodes 3 are formed on
upper surface 2A of piezoelectric substrate 2 by sputtering with a
photolithographic technique using resist. Internal electrodes 4 are
formed on upper surface 2A. Then, anti-corrosion layer 15 is formed
on upper surface 4A of internal electrode 4 by a vapor deposition
method.
Next, as shown in FIG. 2B, photosensitive polyimide-based resin 16
is formed entirely on upper surface 2A of piezoelectric substrate 2
for covering IDT electrodes 3 and internal electrodes 4 by a
spin-coating method, dispensing method, or screen printing method.
The spin-coating method among others is preferable because this
method provides the film with a uniform thickness.
Next, the resin is exposed and developed from upper surface 2A, and
is then, thermally hardened to form side walls 5 surrounding IDT
electrodes 3, as shown in FIG. 2C. After forming walls 5 having a
predetermined shape, side wall 5 is heated if necessary for
accelerating the hardening of the material.
Then, as shown in FIG. 2D, metal foil 17 to be lid 7 is adhered
onto upper surfaces 5A of side walls 5 with adhesive agent 18.
Metal foil 17 is patterned to have a predetermined shape by etching
with a photolithographic method using a resist, and then, the
resist is removed. Then, an unnecessary portion of adhesive agent
18 is removed by a dry etching method, thus covering space 8 above
IDT electrodes 3 with lid 7 and adhesive layer 66, as shown in FIG.
2E. No portion of lid 7 or adhesive layer 66 remains preferably
entirely on upper surfaces 5A of walls 5. In other words, viewing
from top, lid 7 and adhesive layer 66 are preferably located inside
the outer edge of upper surfaces 5A connected with outer side
surfaces 5D of wall 5. Lid 7 and adhesive layer 66 protruding
outward from upper surfaces 5A in view from top prevent base layer
19 which is supposed to be formed by sputtering after this step
from adhering to the boundary between anti-corrosion layer 15 and
outer side surfaces 5D or side walls 5.
Next, as shown in FIG. 2F, base layer 19 is formed entirely on
upper surface 2A of piezoelectric substrate 2 by sputtering.
Portion 19D of layer 19 is provided on outer side surface 5D of
wall 5. Portion 19C of layer 19 is provided on upper surface 4A of
internal electrode 4. Portions 19D and 19C of base layer 19
constitute electrode base layer 9. Portion 19E of base layer 19
provided on upper surface 7A of lid 7 constitutes lid base layer
13.
Electrode base layer 9 is not formed in holes of side walls 5 by
sputtering but is formed on the partially exposed peripheries of
walls 5. This structure prevents electrode base layer 9 from
breaking, thereby preventing connection electrode 12 supposed to be
formed by the electrolytic plating process in the next step from
breaking.
Then, a resist is formed on portions to grow due to the
electrolytic plating by photolithographic technique. Specifically,
the resist exposes, from the resist, portions 19C and 19D to be
electrode base layer 9 and portion 19E to be lid base layer 13, and
is formed to cover the other portion of base layer 9. Then, the
first electrolytic plating with a plating solution is performed so
that a portion of connection electrode 12 can be formed on
electrode base layer 9. At this moment, lid reinforcing layer 14 is
formed on lid base layer 13. Thus, lid reinforcing layer 14
reinforces lid 7, and can be formed simultaneously to connection
electrode 12, hence efficiently producing lid reinforcing layer
14.
Next, a resist is formed entirely on a main surface of
piezoelectric substrate 2 except a space above connection electrode
12. The resist is formed also on upper surface 14A of lid
reinforcing layer 14. Then, the second electrolytic plating with a
plating solution is performed so that the resist forming the
connection electrode 12 can develop upward above the resist. Then,
the resist is removed, as shown in FIG. 2G.
In the case that lid 7 is mechanically strong, lid reinforcing
layer 14 is not necessarily formed. Then, only the first
electrolytic plating is needed for forming connection electrode
12.
In FIG. 2G, connection electrodes 12 are separated from lid
reinforcing layer 14. However, the resist between at least one of
connection electrodes 12 and lid reinforcing layer 14 can be
removed so that connection electrodes 12 can be connected to lid
reinforcing layer 14 during the first electrolytic plating process.
This structure prevents lid 7 and layer 14 from floating
electrically to stabilize electric potentials of these elements. In
particular, the connection between lid 7, lid reinforcing layer 14
and connection electrode 12, which functions as a grounding
terminal, allows lid 7 and lid reinforcing layer 14 to be at the
ground potential, so that lid 7 and lid reinforcing layer 14 can
function as a shielding layer that protects IDT electrode 3 from
noises.
Lid reinforcing layer 14 conductive to connection electrode 12 via
base layer 19, however, is disconnected from electrode 12 so that
they can be isolated electrically from each other, as shown in FIG.
2H. In this case, base layer 19 is removed by etching. In the case
that lid reinforcing layer 14 is intentionally connected to
electrode 12 by plating, base layer 19 provided between lid
reinforcing layer 14 and electrode 12 is not removed.
As shown in FIG. 2I, insulator 10 is formed by a printing method
for covering the main surface of piezoelectric substrate 2 and
elements placed on the main surface while upper surfaces 12A of
connection electrodes 12 are exposed. In order to allow insulators
10 to have a height identical to that of connection electrodes 12,
insulator 10 is formed temporarily to have a height larger than
that of upper surfaces 12A of electrodes 12, then is ground off
mechanically. In this case, insulator 10 is formed to cover
everything on upper surfaces 2A including electrodes 12, and then,
is ground off mechanically. However, the height of insulators 10
can be hardly identical to that of electrodes 12 without grinding
off electrodes 12. This mechanical grinding of insulators 10 thus
involves grinding off of electrodes 12 partly. Considering this
fact, connection electrodes 12 is preferably formed by the
electrolytic plating process to have a height slightly larger than
the height actually required. The grinding off of insulators 10 and
electrodes 12 allows the heights of these elements to be identical
to each other, and achieves a great flatness, so that acoustic wave
device 1 can have a desirable shape to be mounted on a board.
The resist formed after the first electrolytic plating process can
be used as insulator 10 on lid reinforcing layer 14.
Finally, as shown in FIG. 2J, external electrodes 11 are formed on
upper surfaces 10A of insulators 10. External electrodes 11 are
connected electrically to upper surfaces 12A of connection
electrodes 12. Then, piezoelectric substrate 2 and insulator 10 are
divided simultaneously by dicing, thereby providing individual
chips of acoustic wave device 1 from an assembled board.
Next, acoustic wave device 1 in accordance with Embodiment 1 used
in an acoustic wave filter having a pattern in which internal
electrode 4 and side wall 5 are placed will be described below with
reference to FIGS. 3 and 4.
FIG. 3 is a top view of acoustic wave filter 2001 in accordance
with Embodiment 1 for illustrating the arrangement of internal
electrode 4 and side wall 5. As shown in FIG. 3, internal
electrodes 4 are not shown partly since side wall 5 hides them. Lid
7, electrode base layer 9, insulator 10, connection electrode 12
and others are omitted in FIG. 3 in order to illustrate the pattern
of internal electrode 4 and side wall 5 more conspicuously.
Acoustic wave filter 2001 includes two internal electrodes 54A to
be used as pad (hereinafter referred to as internal electrodes 54A
for pad), plural IDT electrodes 53A connected in series via
internal electrodes 54B for wiring between the two internal
electrodes 54A for pad, internal electrode 54C for grounding
connected to a grounding terminal, and IDT electrodes 53B connected
in parallel between internal electrode 54C for grounding and
internal electrode 54B for wiring.
Internal electrodes 54A for pad, internal electrodes 54B for
wiring, IDT electrodes 53A connected in series, internal electrodes
54C for grounding, and IDT electrodes 53B connected in parallel are
provided on upper surface 2A of piezoelectric substrate 2. Two
internal electrodes 54A for pad are connected to input-output
terminals. Internal electrodes 54A for pad, internal electrodes 54B
for wiring, and internal electrodes 54C for grounding are internal
electrode 4 shown in FIG. 1B. IDT electrodes 53A connected in
series and IDT electrodes 53B connected in parallel are IDT
electrode 3 shown in FIG. 1B.
As shown in FIG. 3, anti-corrosion layers 15 provided between
internal electrodes 54A for pad and side wall 5 are placed such
that layers 15 protrudes to outer side walls 5D of wall 5 in view
from top.
FIG. 4 is a top view of acoustic wave filter 2002 in accordance
with Embodiment 1 for illustrating the arrangement of internal
electrodes 4 and side wall 5. In FIG. 4, internal electrodes 4 are
not shown partly since side wall 5 hides them. Lid 7, electrode
base layer 9, insulator 10, connection electrode 12 and others are
omitted in order to illustrate the arrangement of internal
electrode 4 and side wall 5 more conspicuously.
Side wall 5 has holes 5F located above internal electrodes 54A for
pad. The connection electrodes pass through holes 5F.
Anti-corrosion layer 15 formed between electrode 54A and wall 5
protrudes to inside hole 5F in view from top.
Anti-corrosion layer 15 formed between electrode 54A and wall 5 is
less soluble in the plating solution which is used in the
electrolytic plating process for forming connection electrodes 12
than internal electrode 54A(4) is. A void is produced between side
wall 5 and internal electrodes 54A for pad, so that the electrode
base layer may not adhere securely to the boundary between wall 5
and electrodes 54A. Even in this case, anti-corrosion layer 15
between electrodes 54A and wall 5 prevents electrodes 54A from
being corroded during the electrolytic plating process. This
prevents electrodes 54A(4) from breaking, and increases the yield
rates of acoustic wave filters 2001 and 2002.
Acoustic wave device 1 in accordance with Embodiment 1 can be used
not only in a ladder-type filter but also in other types of
filters, such as DMS filter.
According to Embodiment 1, the structure of acoustic wave device 1
and the method for manufacturing thereof are demonstrated. The
method for forming connection electrode 12 described in the
foregoing structure and the manufacturing method are applicable to
the manufacturing of electronic components, such as semiconductor
chips, other than the acoustic wave device.
Exemplary Embodiment 2
FIG. 5A is a plan view of acoustic wave device 1001 in accordance
with Exemplary Embodiment 2 of the present invention. FIG. 5B is a
sectional view of acoustic wave device 1001 on line 5B-5B shown in
FIG. 5A.
Acoustic wave device 1001 is a chip-size packaged device and
includes piezoelectric substrate 2, interdigital transducer (IDT)
electrode 3 provided on upper surface 2A of substrate 2, and
insulator 10 provided on upper surface 2A of piezoelectric
substrate 2 for covering and protecting IDT electrode 3 from the
outside.
Acoustic wave device 1001 further includes internal electrode 4
provided on upper surface 2A of piezoelectric substrate 2, side
wall 5 provided on upper surface 2A of piezoelectric substrate 2 or
on upper surface 4A of internal electrode 4, i.e., above upper
surface 2A of piezoelectric substrate 2 or above upper surface 4A
of internal electrode 4, and lid 7 provided on upper surface 5A of
side wall 5 via adhesive layer 66. Internal electrode 4 is
electrically connected with IDT electrode 3. Side wall 5 surrounds
IDT electrode 3 to provide space 8 above IDT electrode 3. Lid 7
covers space 8.
Acoustic wave device 1001 further includes lid base layer 13
provided on upper surface 7A of lid 7, and lid reinforcing layer 14
provided on upper surface 13A of lid base layer 13 and made of
plated metal. Lid reinforcing layer 14 increases the mechanical
strength of lid 7.
Side wall 5 has inner side surface 5C facing space 8 and outer side
surface 5D opposite to inner side surface 5C. Acoustic wave device
1001 further includes side-wall base layer 20 provided on upper
surface 5A and outer side surface 5D of wall 5. Side-wall base
layer 20 is electrically connected with lid base layer 13.
Side-wall base layer 20 is provided also on a portion of upper
surface 2A of substrate 2 opposite to space 8 with respect to side
wall 5, or is provided on a portion of upper surface 4A of internal
electrode 4. opposite to space 8 with respect to side wall 5
Acoustic wave device 1001 further includes side-wall reinforcing
layer 21 made of plated metal for covering outer side surface 5D
and upper surface 5A of wall 5 via side-wall base layer 20.
Side-wall reinforcing layer 21 is electrically connected with lid
reinforcing layer 14.
FIG. 6 is a sectional view of acoustic wave device 1001 on line 6-6
shown in FIG. 5A, and illustrates connection electrodes 12.
As shown in FIG. 6, acoustic wave device 1001 further includes
electrode base layer 9 provided on upper surface 4A of internal
electrode 4 and on outer side surface 5D as well as upper surface
5A of wall 5, connection electrode 12 provided on upper surface 9A
of electrode base layer 9, and external electrode 11 provided on
upper surface 10A of insulator 10. Connection electrode 12 is made
of plated metal and extends through insulator 10 for electrically
connecting external electrode 11 to IDT electrode 3.
Piezoelectric substrate 2 is made of single-crystal piezoelectric
material, such as crystal, lithium tantalite, lithium niobate, or
potassium niobate. Substrate 2 has a thickness ranging from about
100 .mu.m to 350 .mu.m.
IDT electrode layer 3 includes comb-shaped electrodes having a
thickness ranging from about 0.1 .mu.m to 0.5 .mu.m, and is made of
single metal of aluminum, copper, silver, gold, titanium, tungsten,
platinum, chrome, or molybdenum. Layer 3 can be made of alloy
mainly containing at least one of the above metals, or laminated
structure of at least one of the metals.
Internal electrode 4 is a conductor for electrically connecting
external electrode 11 to IDT electrode 3, and is made of single
metal of aluminum, copper, or silver. Electrode 4 can be made of
alloy mainly containing at least one of the above metals, or
laminated structure of at least one of the metals.
Side wall 5 surrounds IDT electrode 3 at least partly, and has a
height ranging from about 5 .mu.m to 15 .mu.m. Side wall 5 is made
of insulating material, and preferably made of resin since resin
can be processed to have a predetermined shape easily. To be more
specific, photosensitive resin, such as photosensitive polyimide
resin, photosensitive epoxy resin, or photosensitive acrylate
resin, provides side wall 5 with a predetermined shape accurately,
which is necessary to form plural acoustic wave devices 1 on
piezoelectric substrate 2. Photosensitive polyimide resin is
preferable among others for side wall 5 since this resin has a high
glass transitional point and high reliability in a high temperature
environment.
Lid 7 is a plate having a thickness ranging from 1 .mu.m to 10
.mu.m and is bonded to upper surface 5A of side wall 5 with
adhesive layer 66. Lid 7 together with piezoelectric substrate 2
and side wall 5 accommodates IDT electrode 3. Lid 7 is preferably
made of metal because of its excellent mechanical strength and
electrical conductivity that allows controlling electrical
potential of lid 7. Copper is preferable as the material for lid 7
since copper has a liner expansion coefficient similar to that of
single crystal piezoelectric substrate 2. Lid 7 can have a foil
shape. In this case, adhesive layer 66 is formed in advance, and
then lid 7 is stuck on the upper surface of side wall 5. This
structure allows acoustic wave device 1 to be handled easily in the
manufacturing processes.
Space 8 is an airtight area surrounded by piezoelectric substrate
2, side wall 5, and lid 7, and accommodates IDT electrode 3
therein. Space 8 can be filled with air at a normal atmospheric
pressure; however, space 8 is preferably sealed and decompressed to
a pressure lower than the atmospheric pressure since this condition
prevents the IDT electrode from corrosion.
Electrode base layer 9 is made of metallic thin film and formed on
upper surface 4A of internal electrode 4 and outside of side wall
5, i.e. opposite to space 8 with respect to wall 5. Electric base
layer 9 is also formed on outer side surface 5D of side wall 5.
Electric base layer 9 is made of single metal of titanium, copper,
nickel, chrome, or magnesium. Electric base layer 9 can be made of
alloy mainly containing at least one of the above metals. These
materials are less soluble in plating solution than the material of
internal electrode 4. Titanium among others is preferable for
Electric base layer 9 because of its excellent adhesive properties.
Electric base layer 9 can have a double-layer structure including a
titanium layer and a copper layer provided on the titanium layer.
The titanium layer is provided on upper surface 4A of internal
electrode 4, upper surface 15A of anti-corrosion layer 15, and
outer side surface 5D of side wall 5. This structure allows
connection electrode 12 to be formed easily.
Insulator 10 is placed on upper surface 2A of piezoelectric
substrate 2 and outer side surface 5D of side wall 5, and on upper
surface 5A of wall 5 and upper surface 7A of lid 7. Insulator 10
covers lid reinforcing layer 14 and side-wall reinforcing layer 21.
Insulator 10 covers upper surface 2A, a main surface of
piezoelectric substrate 2, thereby protecting IDT electrode 3 and
others from mechanical shocks and moisture. Insulator 10 covers lid
7 and lid-reinforcing layer 14. Insulator 10 is preferably made of
thermosetting resin because of its excellence in handling. Epoxy
resin is preferable because of its heat resistance and
air-tightness. Epoxy resin containing inorganic filler is more
preferable since it has a low linear expansion coefficient. The
inorganic filler may contain aluminum oxide powder, SiO.sub.2
powder, or MgO powder.
External electrode 11 is formed on upper surface 10A of insulator
10 and is electrically connected with connection electrode 12.
According to Embodiment 2, insulator 10 is formed between external
electrode 11 and side wall 5 so as to prevent electrode 11 from
directly contacting side wall 5.
Connection electrode 12 is formed by an electrolytic plating
process on internal electrode 4 via electrode base layer 9.
Connection electrode 12 is preferably made of copper since copper
has a large mechanical strength and has a linear expansion
coefficient matching that of piezoelectric substrate 2. Connection
electrode 12 is electrically connected with internal electrode 4.
In the case that connection electrode 12 is connected to an
input/output terminal, connection electrode 12 is isolated
electrically from lid 7, lid base layer 13, lid reinforcing layer
14, and side-wall base layer 20. In the case that connection
electrode 12 is connected to a grounding terminal, connection
electrode 12 connected to lid 7, lid base layer 13, lid reinforcing
layer 14, and side-wall base layer 20 stabilizes a grounding
potential.
Lid base layer 13 is formed on lid 7 and made of metal thin film.
This metal is at least single metal of titanium, copper, nickel,
chrome, or magnesium. The metal can be made of alloy mainly
containing at least one of the above metals. Titanium among others
is preferable for lid base layer 13 because of its excellent
adhesiveness. Lid base layer 13 can have a double-layer structure
including a titanium layer and a copper layer similar to the
structure of electrode base layer 9 shown in FIG. 1C. This
structure preferably allows lid reinforcing layer 14 to be formed
easily. Lid base layer 13 functions as a base coat for the
electrolytic plating.
Lid reinforcing layer 14 is formed by the electrolytic plating
process on upper surface 13A of lid base layer 13, and has a
thickness ranging from about 20 .mu.m to 40 .mu.m. Lid reinforcing
layer 14 can be preferably made of single metal of copper, gold,
silver, platinum, or nickel. Layer 14 can be made of alloy mainly
containing at least one of the above metals. Copper is preferable
because copper has a large mechanical strength and has a linear
expansion coefficient matching that of piezoelectric substrate
2.
Side-wall base layer 20 is made of metal thin film formed on upper
surface 2A of piezoelectric substrate 2, on outer side surface 5D
and upper surface 5A of side wall 5. Side-wall base layer 20 can be
made of single metal of titanium, copper, nickel, chrome, or
magnesium. Side-wall base layer 20 can be made of alloy mainly
containing at least one of the above metals. The foregoing
materials are less soluble in the plating solution than the
material of internal electrode 4. Titanium among others is
preferable for layer 20 because of its excellent adhesiveness.
Side-wall base layer 20 can have a double-layer structure including
a titanium layer and a copper layer similar to the structure of
electrode base layer 9 shown in FIG. 1C. This structure preferably
allows side-wall reinforcing layer 21 to be formed easily.
Side-wall reinforcing layer 21 is electrically connected with lid
reinforcing layer 14 and covers side-wall base layer 20. Side-wall
reinforcing layer 21 is formed by the electrolytic plating process
and has a thickness ranging from about 20 .mu.m to 40 .mu.m.
Side-wall reinforcing layer 21 can be preferably made of single
metal of copper, gold, silver, platinum, or nickel. Side-wall
reinforcing layer 21 can be made of alloy mainly containing at
least one of the above metals. Copper is preferable because copper
has a large mechanical strength and has a linear expansion
coefficient matching that of piezoelectric substrate 2. In FIG. 5B,
side-wall reinforcing layer 21 is formed on outer side surface 5D
and upper surface 5A of wall 5. In the case that lid 7 is formed
entirely on upper surface 5A, side-wall reinforcing layer 21 can be
formed only on outer side surface 5D.
Side-wall reinforcing layer 21 is made of plated metal, and
prevents moisture from entering space 8 via side wall 5 from the
outside of acoustic wave device 1001 so as to prevent aged
deterioration in characteristics of acoustic wave device 1001.
Side-wall reinforcing layer 21 can increase the mechanical strength
of side wall 5, and improves the anti-shock property of acoustic
wave device 1001 accordingly.
A method for manufacturing acoustic wave device 1001 in accordance
with Embodiment 2 will be described below. FIGS. 7A to 7I are
sectional views of acoustic wave device 1001 for schematically
illustrating processes for manufacturing acoustic wave device
1001.
First, as shown in FIG. 7A, plural IDT electrodes 3 are formed on
upper surface 2A of piezoelectric substrate 2 by sputtering with
photolithographic technique using a resist. Internal electrodes 4
are formed on upper surface 2A by a vapor deposition method.
Next, as shown in FIG. 7B, photosensitive polyimide-based resin 16
is applied entirely onto upper surface 2A of piezoelectric
substrate 2 for covering IDT electrodes 3 and internal electrodes 4
by a spin-coating method, dispensing method, or screen printing
method. The spin-coating method among others is preferable because
this method provides the resin with a uniform thickness.
Next, the applied resin is exposed and developed through a
predetermined mask from upper surface 2A, and then is thermally
hardened to form side walls 5 which surround IDT electrodes 3 as
shown in FIG. 7C. After forming walls 5 to have a predetermined
shape, walls 5 are heated if necessary for accelerating the
hardening of the walls.
As shown in FIG. 7, metal foil supposed to be lid 7 is stuck to the
upper surface of side wall 5 via adhesive agent 18, and then, metal
foil 17 is etched through a resist by the photolithographic method,
thereby patterning metal foil 17 having a predetermined shape.
Then, the resist is removed. An unnecessary portion of adhesive
agent 18 is removed by a dry etching method. These processes
provides space 8 above IDT electrode 3 to be covered with lid 7 and
adhesive layer 66, as shown in FIG. 7E. No portion of lid 7 or
adhesive layer 66 preferably remains entirely on upper surface 5A
of side wall 5. In other words, lid 7 and adhesive layer 66 are
preferably formed inside an outer edge where upper surface 5A is
connected with outer side surface 5D of side wall 5 in view from
top. If lid 7 and adhesive layer 66 protrude outward from upper
surface 5A in view from top, base layer 19, to be formed by
sputtering after this process is prevented from adhering to outer
side surfaces 5D or upper surface 5A of side wall 5.
Next, as shown in FIG. 7F, base layer 19 is formed entirely on
upper surface 2A of piezoelectric substrate 2 by sputtering.
Portions 119 and 219 of base layer 19 formed on outer side surface
5D of wall 5 and on upper surface 2A of substrate 2 constitute
side-wall base layer 20. Portion 319 of base layer 19 formed on
upper surface 7A of lid 7 constitutes lid base layer 13.
Then, a resist is formed by photolithographic technique on portions
of base layer 19 other than a portion where the electrolytic
plating grows. To be more specific, the resist exposes a portion of
the upper surface of base layer 19 to be side-wall base layer 20 as
well as a portion of the upper surface of base layer 19 to be lid
base layer 13, and the resist covers the other portions. Then, the
first electrolytic plating is performed so that side-wall
reinforcing layer 21 can be formed on side-wall base layer 20. At
this moment, lid reinforcing layer 14 is formed on lid base layer
13. Then, the resist is removed, as shown in FIG. 7G. Lid
reinforcing layer 14 and side-wall reinforcing layer 21 reinforce
lid 7 and side wall 5, respectively. Lid reinforcing layer 14 and
side-wall reinforcing layer 21 reinforce lid 7 are formed
simultaneously, thus forming side-wall reinforcing layer 21
efficiently.
Then, a resist is formed entirely on upper surface 2A of
piezoelectric substrate 2 except a portion where connection
electrode 12 is formed. This resist is also on the upper surface of
lid reinforcing layer 14 and the upper surface of side-wall
reinforcing layer 21. Then, the second electrolytic plating is
performed, so that connection electrode 12 can extend to have a
height greater than that of the resist, and then, the resist is
removed.
The resist between at least one of connection electrodes 12 and lid
reinforcing layer 14 or side-wall reinforcing layer 21 can be
removed so that connection electrodes 12 can be connected with lid
reinforcing layer 14 or side-wall reinforcing layer 21 during the
first electrolytic plating step. This structure prevents lid 7 and
lid reinforcing layer 14 or side-wall reinforcing layer 21 from
floating electrically, and stabilizes electric potentials of them.
In particular, lid 7, lid reinforcing layer 14 or side-wall
reinforcing layer 21 can be connected with connection electrode 12
functioning as a grounding terminal to provide lid 7 and lid
reinforcing layer 14 or side-wall reinforcing layer 21 with a
ground potential, so that lid 7 and lid reinforcing layer 14 and
side-wall reinforcing layer 21 can function as shielding layers
that protect IDT electrode 3 from noises.
As shown in FIG. 7H, base layer 19 is removed partly by etching so
that side-wall base layers 20 are isolated electrically from each
other. In the case that lid reinforcing layer 14 or side-wall
reinforcing layer 21 is connected to connection electrode 12 by
plating, a portion of base layer 19 existing between connection
electrode 12 and lid reinforcing layer 14 or side-wall reinforcing
layer 21 is not removed.
As shown in FIG. 7I, insulator 10 is formed by a printing method to
cover the main surface, upper surface 2A of piezoelectric substrate
2 and elements placed on upper surface 2A. In order to provide
insulator 10 with a height identical to that of connection
electrodes 12, insulator 10 is formed temporarily to have a height
greater than that of upper surfaces 12A of electrodes 12, and then,
is ground off mechanically. In this case, insulator 10 is formed to
cover all components, such as electrodes 12, located on upper
surfaces 2A, and then ground off mechanically. The height of
insulator 10 can hardly be identical to that of electrodes 12
without the grinding off electrodes 12 at all while insulator 10 is
ground off. Therefore, electrodes 12 are ground off partly with the
grinding off of insulator 10. Considering this fact, connection
electrodes 12 are preferably formed by the electrolytic plating
process to have a height slightly greater than the actually
required height. Then, insulator 10 and electrodes 12 are ground to
allows the heights of them to be identical to each other, thus
providing a flatness, so that acoustic wave device 1001 can have a
shape suitable to be mounted on a board.
The resist formed after the first electrolytic plating process can
be used as insulator 10 on lid reinforcing layer 14 and side-wall
reinforcing layer 21.
Finally, external electrodes 11 connected electrically to the upper
surfaces of connection electrodes 12 are formed. Then,
piezoelectric substrate 2 and insulator 10 are divided
simultaneously by dicing, thereby providing individual chips of
acoustic wave device 1001 from an assembled board.
Next, the arrangement internal electrode 4 and side wall 5 of
acoustic wave device 1001 in accordance with Embodiment 2 used in
an acoustic wave filter will be described below with reference to a
figure.
FIG. 8A is a top view of acoustic wave filter 2003 in accordance
with Embodiment 2 for illustrating the arrangement of internal
electrode 4, side wall 5, and side-wall reinforcing layer 21. In
FIG. 8A, internal electrodes 4 are not shown partly since side wall
5 hides them. Lid 7, electrode base layer 9, insulator 10,
connection electrode 12 and others are omitted in order to
illustrate the arrangement of internal electrode 4, side wall 5 and
side-wall reinforcing layer 21 conspicuously.
Acoustic wave filter 2003 includes two internal electrodes 54A for
pad connected to input/output terminals, plural IDT electrodes 53A
connected in series via internal electrodes 54B for wiring between
the two internal electrodes 54A for pad, internal electrode 54C for
grounding connected to a grounding terminal, and IDT electrodes 53B
connected in parallel between internal electrode 54C for grounding
and internal electrode 54B for wiring.
Two internal electrodes 54A for pad, internal electrodes 54B for
wiring, plural IDT electrodes 53A connected in series, internal
electrodes 54C for grounding, and IDT electrodes 53B connected in
parallel are provided on upper surface 2A of piezoelectric
substrate 2. Internal electrodes 54A for pad, internal electrodes
54B for siring, and internal electrodes 54C for grounding are
internal electrode 4 shown in FIGS. 5B and 6. Plural IDT electrodes
53A connected in series and IDT electrodes 53B connected in
parallel are IDT electrode 3 shown in FIGS. 5B and 6.
As shown in FIGS. 5B and 8A, side-wall reinforcing layer 21 placed
at the periphery of side wall 5 includes portion 121 covering outer
side surface 5D and portion 221 covering upper surface 5A of wall
5.
Side-wall reinforcing layer 21 is made of plated metal, and prevent
moisture from entering space 8 via side wall 5 from the outside of
acoustic wave device 1001, preventing aged deterioration in
characteristics of device 1001.
Side-wall reinforcing layer 21 can increase the mechanical strength
of side wall 5, thereby improving the anti-shock property of device
1001.
Acoustic wave device 1001 in accordance with Embodiment 2 can be
used not only in ladder-type filters but also in other types of
filter, such as DMS filters.
FIG. 8B is a block diagram of electronic apparatus 3001 in
accordance with Embodiments 1 and 2. Electronic apparatus 3001 is a
communication apparatus and includes acoustic wave filter 2001
(2002, 2003), semiconductor integrated circuit (IC) 3002 connected
to acoustic wave filter 2001 (2002, 2003), and demodulator 3003
connected to semiconductor IC 3002. Acoustic filter 2001 (2002,
2003) provides electronic apparatus 3001 with high communication
quality.
Acoustic wave devices 1 and 1001 prevent internal electrode 4 from
breaking with the plating solution, and can be used in electronic
apparatuses such as a mobile communication apparatus.
According to Embodiments 1 and 2, terms, such as "upper surface"
and "lower surface", indicating directions indicate relative
directions depending only on the relative positional relation
between structural elements, such as the piezoelectric substrate,
the IDT electrode, of the acoustic wave device, and do not indicate
absolute directions, such as a vertical direction.
* * * * *